Type ignition circuit condenser discharge



April 28, 1964 H. P. QUINN 3,131,327

TYPE IGNITION CIRCUIT CCNDENSER DISCHARGE 2 Sheets-Sheet l Filed NOV. 21, 1960 D/sz- I'll-qrllkllullllllll rl l hl l l llln i Tic W10 VOL 779%5 HRNLI/ VBY T KM ATTORNEYS April 28, 1964 H. P. QUINN I TYPE IGNITION CIRCUIT CONDENSER DISCHARGE 2 Sheets-Sheet 2 Filed NOV. 21, 1960 T '1 Comma-s INVENTOR A544 say f"? Qwxwv BY I MWQLM 5 ATTORNEYS United States Patent 3,131,327 TYPE IGNHTIQN CTR-CUT! CONDENSER DES-CHARGE Haisey P. Quinn, Whippany, Ni, assignor to Tang-Sol Eiectric Inc, a corporation of Delaware Filed Nov. 21, 196-9, Ser. No. 719,889 19 Claims. (82. 31-=-177) This invention relates to an ignition circuit for internal combustion engines and has particular reference to a circuit which generates a high voltage pulse without drawing excessive current through the breaker points.

The use of higher compression ratios in the modern automobile and truck engines requires a higher voltage at the points of the spark plugs and greater dependability of the remaining circuit components. Several attempts have been made to achieve the required results by combining transistor amplifiers with gaseous discharge tubes and storage capacitors but these circuits have been expensive, buiky, and sometimes refuse to operate when one spark plug is short circuited or refuses to fire because of too Widely separated points. The present invention utilizes relatively few elements, insures a strongly peaked sparking voltage pulse that causes a discharge at some of the spark plugs even though other plugs are disconnected or shorted.

The new i nition circuit for high compression engines is relatively inexpensive as compared to those heretofore proposed. It increases the life of spark plugs and reduces, if not eliminates, misfiring due to fouled plugs by providing a single high voltage pulse across the spark plug terminals. The circuit effectively reduces the required current through the breaker contacts thus insuring longer contact life.

In the preferred embodiment of the invention the usual pair of breaker contacts is connected in series with a storage battery and the input circuit of a current amplifier. The breaker contacts are controlled to open and close in synchronism with the movements of the engines pistons. The output or" the amplifier is connected to an inductor which stores the energy of the current pulses in the inductors magnetic field. The stored energy in the inductor is transferred to a storage capacitor. Voltage for the spark plugs is obtained by discharging the capacitor through a unidirectional device and the primary winding of an output transformer, the secondary winding of which may be connected to the spark plugs through the usual rotatable distributor head.

For a better understanding of the present invention, together with various embodiments thereof, reference may be made to the following description taken in connection with the accompanying drawings.

FIG. 1 is a schematic diagram of connections of the preferred form of the ignition circuit of the invention;

FIG. 2 is a schematic diagram of connections similar to FIG. 1 but employing a different type of transistor amplifier;

FIG. 3 is a graph showing some of the currents and voltages during the operation of the circuit shown in FIG. 1;

FIG. 4 is a schematic diagram of connections of an ignition circuit employing two transistors and a separate inductor;

FIG. 5 is a schematic diagram of connections similar to FIG. 4 but arranged to operate without a separate inductor;

1G. 6 is a graph showing some of the currents and volt-ages 'as they occur in the circuit shown in FIG. 4 during its operation; and

FIG. 7 is a schematic diagram representing a modified form of ignition circuit embodying the invention.

3,131,327 Patented Apr. 28, 1964 Referring now to FIG. 1, the circuit includes the usual storage battery 10 and breaker contacts 11 which are operated by a portion of the mechanical gearing coupled to the engine drive shaft. A transistor amplifier 12 in cludes a single p-n-p transistor 13 with its base connected to one of the contacts 11 through a limiting resistor 14 and its collector connected to the negative battery terminal through another limiting resistor 15.

The emitter of the transistor connected through a primary winding 16 of an induction coil 17, and a limiting resistor 56 to a switch contact 57 of a switch 58. The movable contact arm of the switch 58, which is connected to the positive terminal of the battery, is placed in engagement with contact 57 during running condition of the engine and during such condition the above described connection from the emitter including winding 16 and resistor 56 represents the output circuit of the transistor amplifier. During starting conditions, when the drain on the battery reduces its voltage, the contact arm of the switch 58 is placed in engagement with a contact 59 which is connected directly to one end of a second primary winding 60 of the induction coil, the other end of winding 60 being connected to winding 16. Thus during starting the transistor output circuit includes additional turns of the induction coil and the circuit resistance is reduced by elimination of resistor 56. Although not shown in the diagram, switch 58 could, and preferably would, be relay operated from the usual starting relay.

Inductance coil 17 includes two secondary windings 1'8 and 20. Winding 18 transfers the energy stored in the coil to a capacitor 21 and this secondary winding 18 is connected in series with a rectifier 38 and the primary winding 24 of an output transformer 25. When capacitor 21 is being charged, the charging circuit includes secondary winding 18, rectifier 38, capacitor 21, and the primary winding 24. When capacitor 21 is being discharged, -the circuit includes the capacitor, the anodecathode circuit of a gaseous discharge device 23, and the primary winding 24 of the output transformer. The output circuit includes the usual plurality of spark plugs represented by a single gap 26 is FIG. 1 and a distributor 27 which may be operated by a mechanical gear means coupled to the drive shaft. The operation of the distributor and the spark plugs are well known and need not be described here in detail.

The operation of the charging circuit is as follows: When contact points are open, no current flows through the transistor 13 because the base is disconnected. When contacts 11 close, current is drawn from the battery 10 through winding 16 or through windings 60 and 16, depending upon the position of the contact arm of switch 58, and the transistor amplifier 13 back to the negative terminal of the battery. This current is made possible by the change in potential of the base of transistor 13 and it should be noted that the current through the contact points 11 is a minimum value, only enough to alter the potential of the base. During the time that the contacts remain closed the direct current battery 10 establishes a current in the primary winding or windings and sets up a reservoir of magnetism in the ferro-magnetic core of the coil 17. The currentthrough the base is illustrated in FIG. 3 by the square topped wave forms 30 while the current through primary winding 16 is shown in FIG. 3 by wave forms 31.

When contacts 11 are opened, the current through the transistor output circuit is cut off abruptly and the collapse of the magnetic field in inductance coil 17 sets up an inductive voltage in secondary winding 18 which results in a charging current which can be traced from the upper end of winding 18, through rectifier 38, capaci tor 21, winding 24 and back to the other side of winding 18. This current charges capacitor 21 to a potential of approximately 2000 volts. The capacitor voltage during the charging periods is shown by Wave forms 37 in FIG. 3. The firing electrode 32 is connected through a pair of series connected resistors 61 and 62 to one end of secondary winding 20, resistor 61 being of relatively low resistance compared to resistor 62. During the above described action, a voltage is generated in secondary winding 20 which with the firing electrode circuit so far described, would make the firing electrode assume a negative potential as compared to its cathode. The negative peak voltages of the control grid are shown in the dotted line portions of wave forms 39 of FIG. 3. Discharge device 23 is normally nonconductive and making the firing electrode more negative than its cathode does not change this condition.

However, the peak negative voltage impressed upon the electrode 32 is preferably suppressed by the provision of a rectifier diode 63 connected between the cathode of device 23 and the junction of resistors 61 and 62 and bridged by a capacitor 64, the anode of the diode being connected to the cathode of device 23. The suppression of the negative peak potentials of the grid is shown by the solid line portions of wave forms 39 of FIG. 3.

When contacts 11 are again closed a positive voltage pulse is applied to the firing electrode 32 by winding 2% and the discharge device 23 is made conductive, discharging capacitor 21 through the discharge device and the primary winding 24 of the output transformer. This discharge current is of the order of 150 amperes and this pulse generates a high voltage in secondary winding 33 which is applied to the spark plugs 26 through distributor 27.

If, for any reason, the discharge device 23 does not fire, such as under contact bounce conditions, capacitor 21 will retain its charge. During the next cycle when the energy in the induction coil 17 would normally be transferred to capacitor 21, there is a high voltage developed across the induction coil 17 and also across transistor 13. This voltage may cause serious injury to the transistor and for this reason, an additional primary winding 34 is wound on induction coil 17 and connected at one end to winding 60 and at its other end through a rectifier 35 to the negative terminal of the battery. If the voltage across winding 34 or across windings 60 and 34, depending upon the position of switch 58, is greater than the battery voltage, current is sent through rectifier 35 and absorbs the inductor energy by charging battery 10.

The circuit shown in FIG. 2 is substantially the same as that shown in FIG. 1 except that an n-p-n transistor 36 is used in the positive battery lead, rectifier 35 is reversed and a crystal diode 22 has been substituted for the gas rectifier tube 38. Also the starting circuit has not been specifically shown in FIG. 2 nor have the means in the circuit of the firing electrode for suppressing peak negative voltages. Except for these variations, the operation is substantially the same.

The graph in FIG. 3 shows that the inductor winding 16 receives its charging current when the contacts 11 are closed and that the capacitor 21 is charged during the time interval when the contacts are open. Wave forms 37 show the charging voltage. The spark plugs are fired when the contacts are closed after an initial c cle.

The circuit shown in FIG. 4 is similar to the circuits shown in FIGS. 1 and 2 and includes a transistor amplifier, a storage inductor, a charging circuit which charges a capacitor, and a discharge circuit including a gaseous discharge device. The battery has its positive terminal connected to the emitters of both transistors 40 and 41. The base of the first stage transistor 40 is connected in series with the breaker contacts 11 and when the contacts are open the first transistor does not conduct. The base of the second transistor 41 is connected permanently to the negative terminal of battery 10 through a resistor 42 so that when the contacts are open, current passes through the emitter-collector electrodes and through an inductor 43 in series with a small limiting resistor 44. Current is prevented from passing through primary winding 16 of transformer 17 because of diode rectifier 45. Also, current can not pass through the primary winding 34 of transformer 17 because of diode rectifier 35.

Gaseous discharge device 23 has its firing electrode energized by the secondary winding 46 of a transformer whose primary winding 48 is connected in series with the battery 10 and contacts 11. The windings are arranged so that the closure of the contacts applies a negative voltage to the firing electrode and the nonconducting condition of the device is not changed. When the contacts are open, a positive voltage is applied to the firing electrode and the device 23 is made conductive, discharging the capacitor 21 through the primary winding 24 of output transformer 25 and sending a high voltage pulse to the spark plugs.

The operation of the circuit shown in FIG. 4 is as follows: With the breaker contacts 11 open, transistor 40 is nonconductive permitting transistor 41 to pass current from the positive terminal of the battery through the emitter-collector of transistor 41, resistor 44, inductor winding 43, and back to the negative terminal of battery 10. This current stores magnetic energy in the core of inductor 43. At this time (contacts 11 open), discharge device 23 is made conductive as described above, but, since this is an initial operation and capacitor 21 has not been charged, no current flows through the device.

When the breaker contacts close, transistor 40 is made conductive and passes current through its emitter-collector and resistor 42, thereby increasing the potential at the base of transistor 41 making it nonconductive and cutting off the current through inductor 43. The collapse of the magnetic field of inductor 43 generates a current pulse of opposite polarity which flows through winding 16 and rectifier 45 and generates another current pulse in secondary winding 18 which charges capacitor 21.

When the breaker contacts open again, secondary winding 46 applies a positive voltage to the firing electrode 32, as above described, and the charge on capacitor 21 is discharged, producing the high voltage for the spark plugs. Winding 34 and rectifier 35 clip the over-voltage surge, as described above, only when the tube 23 does not fire.

Thus the operation of the circuit of FIG. 4 difiers from that of FIG. 1 primarily in that the spark plugs are fired when the contacts open whereas in the system of FIG. 1 the spark plugs fire when the contacts close.

The circuit shown in FIG. 5 is the same as the circuit of FIG. 4 except the inductor 43 and the rectifier 45 have been omitted. Primary winding 16 in this circuit takes the place of inductor 43 and when transistor 41 conducts, the current through winding 16 stores energy in its magnetic field. The rise of this current induces a voltage in winding 18 but current is blocked because of rectifier 22. When the current in Winding 16 is abruptly reduced to zero by the closing of contacts 11, a reverse voltage is induced in winding 18 which charges the capacitor 21.

The graph shown in FIG. 6 illustrates the various wave forms generated in the circuit of FIG. 4 and illustrates the timing. Waves 50 are the current pulses in the base circuit of transistor 40. Wave forms 51 are the current pulses in the base circuit of transistor 41 and wave forms 52 represent the current pulses in winding 43.

The capacitor 21 is charged during the time the contacts 11 are closed, this charging voltage shown by wave forms 53, being caused by the current pulses in winding 16 which are shown by wave forms 54. The resultant firing pulse is quite short, only about 1 microsecond, and is illustrated by wave forms 55.

In FIG. 7 a circuit is shown that is similar in some respects to that of FIG. 1 and operating like that of FIG. 4 in that the spark plugs fire when the breaker contacts open. Like the circuit of FIGII a single transistor, indicated at 65 as an n-p-n transistor is employed in the input circuit. The base of transistor 65 is connected directly to one of the breaker contacts 11 and also through current limiting resistor 66 to the positive terminal of battery 10, the cooperating breaker contact being connected to the negative terminal of the battery. The emitter of the transistor 65 is connected to the negative terminal of the battery and the collector of transistor 65 is connected through primary winding 16 of the induction coil 17 and resistor 56 to the positive terminal of the battery. The induction coil 17, as in FIG. 1, includes the primary winding 34 connected to rectifier 35 for protection of the transistor when the capacitor 21 does not discharge. In the particular embodiment of the invention illustrated in FIG. 7 a transistor 67, an n-p-n transistor, is shown in place of the gaseous discharge tube 23 of the other figures. Transistor 67 has its collector connected to the junction between diode 22 and capacitor 21, its emitter connected to ground and its base connected through a resistor 68- to one end of secondary winding 20 of the induction coil 17. The output transformer in FIG. 7 is shown as an auto-transformer 71.

The operation of the circuit of FIG. 7 is substantially like that described in connection with FIGS. 4 and 5. When the breaker contacts are open, transistor 65 conducts because of the connection of its base to the positive terminal of the battery 11). Current thus flows through the winding 16 of the induction coil 17. Transistor 67 at this time is made conductive but as capacitor 21 is not charged no energy is transmitted through the auto-transformer 71 to the spark plugs. When the breaker contacts close the base of transistor 65 is connected directly to the negative terminal of the battery and hence the transistor is made nonconductive. The energy stored in the core of induction coil 17 then discharges through winding 18 and rectifier 38 to charge the condenser 21. During the charging of condenser 21 the base of transistor 67 is made more negative than the emitter and hence no current flows through the collector emitter circuit of that transistor. When the contacts next open to energize the winding 16 the base of transistor 67 is made positive with respect to the emitter and consequently the transistor conducts and discharges capacitor 21 through the autotransformer 71 causing a high potential voltage to be impressed across whichever spark plug is in circuit through the distributor.

Obviously the input circuit of FIG. 7 could be employed with the gas discharge device of FIG. 1 in place of the transistor 67 and conversely the transistor 67 could be substituted for the gas discharge device 23 in the remaining circuits.

Any unidirectional switching device, such as a solid state thyratron, for example a silicon controlled diode, could be employed in the new circuit in place of the gas discharge device of FIGS. 1, 2, 4, 5 and 6 or the transis tor 67 of FIG. 7. Similarly an auto-transformer such as that shown at 71 in FIG. 7 could be provided in any one of the other circuits illustrated in the drawings. In each case also the particular starting circuit of FIG. 1 could be and probably would be employed. For simplic ity the starting circuit has not been shown in FIGS. 2, 4, 5 and 7. The same comments apply to the elements shown in FIG. 1 for suppressing the reverse voltage peaks applied to the triggering electrode of the switch tube. Other variations within the scope of the accompanying claims will occur to those skilled in the art.

The term induction coil is used herein to define a device wherein power is delivered by the secondary when the primary circuit is opened, while the term transformer is used herein to define a device wherein power is delivered by the secondary when the primary circuit is drawing current. Thus in each of the described circuits, except that of FIG. 4, the capacitor is charged from a secondary winding of an induction coil. In FIG. 4

6 because a separate inductor is provided for storing magnetic energy, a transformer is employed to transform the stored energy into a charging current for the capacitor. In each circuit the capacitor discharges through the primary winding of a transformer.

The present application is a continuation-in-part of application Serial No. 13,151 filed March 7, 1960, now abandoned.

The following is claimed:

1. An ignition circuit for internal combustion engines having a spark plug in each combustion chamber, a source of direct current, means connected to said source for creating a series of current pulses synchronized with the movement of the engines pistons, a current amplifier for amplifying pulses created by said means, an inductor coupled to an output circuit of said amplifier for storing energy in the inductors magnetic field, a capacitor coupled to said inductor for receiving a charge therefrom and a discharge circuit which includes said capacitor, a switching device, and an input winding of an output transformer, said output transformer having a winding coupled to said spark plugs.

2. An ignition circuit for internal combustion engines having a spark plug in each combustion chamber comprising, a pair of breaker contacts connected in series with a source of direct current and controlled to open and close in synchronism with the movements of the engines pistons, a transistor amplifier having its input coupled to said source of current and to said breaker contacts for amplifying the current pulses produced thereby, an inductor coupled to an output circuit of said amplifier for storing the current pulse energy received from said amplifier, a capacitor coupled to said inductor for receiving energy therefrom when the current in the inductor is re duced to zero, and a discharge circuit for discharging the capacitor, said discharge circuit including the capacitor, a switching device, and an input winding of an output transformer, said output transformer having a winding coupled to said spark plugs.

3. An ignition circuit as set forth in claim 2 wherein said switching device is a gaseous discharge device having an anode, a cathode, and a firing electrode.

4. An ignition circuit as set forth in claim 3 wherein the anode-cathode path in said gaseous discharge device is normally nonconductive.

5. An ignition circuit according to claim 2 wherein said switching device is a three terminal semiconductor device.

6. An ignition circuit according to claim 5 wherein said switching device is a transistor having a collector, emitter and base electrodes.

7. An ignition circuit for internal combustion engines having a spark plug in each combustion chamber comprising, a pair of breaker contacts connected in series with a source of direct current and controlled to open and close in synchronism with the movements of the engines pistons, an amplifier having its input coupled to said source of current and to said breaker contacts for amplifying the current pulses produced thereby, an inductor including a winding on a ferromagnetic core coupled to an output circuit of said amplifier for storing the current pulse energy received from the amplifier, a capacitor connected to said inductor by means of a coupling circuit for receiving energy therefrom when the current in the inductor is reduced to zero, said coupling circuit including a rectifier, and a discharge circuit for discharging the capacitor, said discharge circuit including the capacitor, a switching device, and an input winding of an output transformer, said output transformer having a winding coupled to said spark plugs.

8. An ignition circuit as set forth in claim 7 wherein said switching device comprises a gaseous discharge device having an anode, a cathode, and a firing electrode, said firing electrode coupled to said coupling circuit for raising the firing electrode potential to a value which is more positive than the cathode potential when said breaker contacts close.

9. An ignition circuit as set forth in claim 8 wherein said coupling circuit includes an induction coil and wherein said inductor is a primary winding on said coil.

10. An ignition circuit as set forth in claim 9 wherein a secondary winding on the induction coil is connected to the cathode and firing electrode of the gaseous discharge device for rendering it conductive.

11. An ignition circuit as set forth in claim 7 wherein said switching device comprises a gaseous discharge device having an anode, a cathode, and a firing electrode, said firing electrode coupled to said coupling circuit for raising the firing electrode potential to a value which is more positive than the cathode potential when said breaker contacts open.

12. An ignition circuit as set forth in claim 11 wherein said coupling circuit includes an induction coil and wherein said inductor is a primary winding on said coil.

13. An ignition circuit as set forth in claim 7 wherein said amplifier includes a transistor having a base, a collector, and an emitter, said base and emitter being connected in series with the breaker contacts and said source of current.

14. An ignition circuit as set forth in claim 7 wherein said switching device is a three terminal semiconductor device having a first terminal connected to said capacitor, a second terminal connected to said primary winding and a third terminal coupled to said coupling circuit, said device being rendered conductive when potential positive with respect to said second terminal is applied to said third terminal.

15. An ignition circuit according to claim 7 wherein said switching device is a three terminal device, two of said terminals being connected in series with said capaci- 8 tor and input winding of said output transformer, the potential of the third terminal of the device controlling conduction between the other two terminals, and means responsive to operation of said breaker contacts for controlling the potential of said third terminal.

16. An ignition circuit according to claim 15 wherein said coupling circuit includes a transformer and said means responsive to operation of said breaker contacts is a secondary winding on said transformer.

17. An ignition device according to claim 15 wherein said coupling circuit includes an induction coil, said inductor comprising a primary winding on said coil, said means responsive to operation of said breaker contacts comprising a secondary winding on said coil.

18. An ignition circuit according to claim 15 including a diode connected between said third terminal and that one of the other two terminals of said device that is connected to the input winding of said output transformer, for suppressing inverse peak voltages applied to said third terminal in response to operation of said breaker contacts.

19. An ignition circuit according to claim 1 wherein said inductor comprises a winding on a ferromagnetic core and including switch means between said source and said inductor for varying the number of turns of said winding in the output circuit of said amplifier for compensating for voltage drop of said source during starting.

References Cited in the file of this patent UNITED STATES PATENTS 2,632,133 McNulty Mar. 17, 1953 2,977,506 Short et al Mar. 28, 1961 2,980,822 Short Apr. 18, 1961 

1. AN IGNITION CIRCUIT FOR INTERNAL COMBUSTION ENGINES HAVING A SPARK PLUG IN EACH COMBUSTION CHAMBER, A SOURCE OF DIRECT CURRENT, MEANS CONNECTED TO SAID SOURCE FOR CREATING A SERIES OF CURRENT PULSES SYNCHRONIZED WITH THE MOVEMENT OF THE ENGINE''S PISTONS, A CURRENT AMPLIFIER FOR AMPLIFYING PULSES CREATED BY SAID MEANS, AN INDUCTOR COUPLED TO AN OUTPUT CIRCUIT OF SAID AMPLIFIER FOR STORING ENERGY IN THE INDUCTOR''S MAGNETIC FIELD, A CAPACITOR COUPLED TO SAID INDUCTOR FOR RECEIVING A CHARGE THEREFROM AND A DISCHARGE CIRCUIT WHICH INCLUDES SAID CAPACITOR, A SWITCHING DEVICE, AND AN INPUT WINDING OF AN OUTPUT TRANSFORMER, SAID OUTPUT TRANSFORMER HAVING A WINDING COUPLED TO SAID SPARK PLUGS. 